Method for the production of a flowable powder of a fluoropolymer compound and flowable powder produced according to the method

Abstract

In order to provide a simple and economical method for the production of a flowable powder of a fluoropolymer compound, there is proposed a method for the production of a flowable powder of a fluoropolymer compound from a dry mixture, which contains at least one fluoropolymer material and at least one filler, including the steps of pressing the dry mixture into lumps and crushing the lumps to form the flowable powder.

1. Method for the production of a flowable powder of a fluoropolymer compound from a dry mixture, which contains at least one fluoropolymer material and at least one filler, comprising the following method steps:
 conveying the dry mixture to a pressing device comprising at least one roller by means of a worm device; 
 pressing the dry mixture into band-shaped lumps by means of the at least one roller of the pressing device; 
 crushing the lumps to form the flowable powder by means of a mill. 
 
   
   
     2. Method according to  claim 1 , wherein the dry mixture has a filler content of 60% by weight at maximum. 
   
   
     3. Method according to  claim 1 , wherein the dry mixture contains polytetrafluoroethylene or modified polytetrafluoroethylene as fluoropolymer material. 
   
   
     4. Method according to  claim 1 , wherein as filler the dry mixture contains an organic filler, an inorganic filler, a mixture of a plurality of organic fillers, a mixture of a plurality of inorganic fillers, and/or a mixture of at least one organic filler and at least one inorganic filler. 
   
   
     5. Method according to  claim 4  wherein the organic filler is selected from the group consisting of PEEK, a polyimide, an aromatic polyester, PPS and PPSO2. 
   
   
     6. Method according to  claim 4  wherein the inorganic filler is selected from the group consisting of glass powder, glass fibres, bronze, carbon, graphite, SiC 2 , Al 2 O 3  and/or MoS 2 . 
   
   
     7. Method according to  claim 1 , wherein the dry mixture has a bulk density of approximately 100 g/l to approximately 1 600 g/l. 
   
   
     8. Method according to  claim 1 , wherein the flowable powder has a bulk density of approximately 400 g/l to approximately 2 500 g/l. 
   
   
     9. Method according to  claim 1 , wherein the flowable powder has a higher bulk density than the dry mixture. 
   
   
     10. Method according to  claim 1 , wherein the fluoropolymer material in the dry mixture has an average grain size d 50  of approximately 5 μm to approximately 100 μm. 
   
   
     11. Method according to  claim 1 , wherein the flowable powder has an average grain size d 50  of approximately 300 μm to approximately 2 500 μm. 
   
   
     12. Method according to  claim 1 , wherein the flowable powder has a higher average grain size d 50  than the fluoropolymer material in the dry mixture. 
   
   
     13. Method according to  claim 1 , wherein the pressing device has two opposing rollers and the worm device extends into the wedge-like region between the opposing rollers. 
   
   
     14. Method according to  claim 1 , wherein the worm device has a substantially vertical rotational axis. 
   
   
     15. Method according to  claim 1 , wherein the worm device is operated at a speed of approximately 10 rpm to approximately 100 rpm. 
   
   
     16. Method according to  claim 1 , wherein the worm device has a pitch that decreases in the transport direction of the worm device. 
   
   
     17. Method according to  claim 1 , wherein the worm device has a diameter that decreases in the transport direction of the worm device. 
   
   
     18. Method according to  claim 1 , wherein the worm device is arranged in a transport chamber, which has at least one groove running in a spiral shape around the transport direction of the worm device. 
   
   
     19. Method according to  claim 1 , wherein the dry mixture is pre-compacted before pressing. 
   
   
     20. Method according to  claim 1 , wherein the dry mixture is at least partially deaerated before pressing. 
   
   
     21. Method according to  claim 1 , wherein the roller is operated with a specific contact force of approximately 1 kN/cm to approximately 10 kN/cm. 
   
   
     22. Method according to  claim 1 , wherein the roller is operated at a speed of approximately 5 rpm to approximately 15 rpm. 
   
   
     23. Method according to  claim 1 , wherein the roller is provided with a profiled rolling surface. 
   
   
     24. Method according to  claim 1 , wherein the relative density of the lumps produced by pressing the dry mixture amounts to approximately 1.3 g/cm 3  to approximately 4.0 g/cm 3 . 
   
   
     25. Method according to  claim 1 , wherein the lumps are crushed by means of a screen type mill. 
   
   
     26. Method according to  claim 1 , wherein the mill is operated at a speed of approximately 60 rpm to approximately 400 rpm.